Modelling of a Spark Ignition Engine with Turbo-Generator for Energy Recovery
To be published on September 9, 2019 by SAE International in United States
Increasingly stringent regulations in the field of pollutant and CO2 are forcing engine manufacturers to adopt new solutions to contain exhaust emissions, such as Hybrid Electric Vehicles (HEV) or Full Electric Vehicles (FEV). Still far from the wide diffusion of FEV limited from electrochemical storage systems together with the difficulty of creating adequate infrastructure distributed throughout the territory to recharging batteries, at present HEVs seems to be a better solution. The hybrid vehicle is already able to guarantee satisfactory autonomy and low pollution levels by combining the advantages offered by the two technologies of thermal and electric propulsion. Currently on the market there are several types of hybrid vehicles, with different degree of hybridization (depending of the electric power of the motor generators installed), capacity to store electricity and type of scheme constructive adopted for the integration between the thermal engine and the electric machines. A particular interest is getting the mild-hybrid (or light hybridization) and the micro-hybrid (or minimum hybridization) with 48V electrical system added to the common 12V one. In this field, a possible application is represented by the electric turbo-compounding system, where a turbine coupled to a generator (turbo-generator) uses the exhaust gas flow of a reciprocating engine to convert waste heat energy into electrical power. In this way, the power generated from the system can be used to feed local electrical loads such as engine auxiliaries, increasing the whole system efficiency. The present study deals with the simulation of a spark ignition engine including a turbo-generator at the exhaust to evaluate the advantages in terms of overall efficiency. The internal combustion engine model was developed by using a 1D code (GT-Power software), while the turbo-generator and the electric system are described in the Matlab/Simulink environment. The results obtained showed an appreciable increase in the overall efficiency.